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Geological Technics ltm Page 6 Groundwater Monitoring Report ' Project No 724 2 April 25,2006 • Figure 6 illustrates the distribution of TPH-G in the intermediate wells A localized high is centered in well MW-108 that extends to the southwest toward MW-106 The concentrations attenuate laterally to the west, southwest and southeast • Figure 7 illustrates the distribution of TPH-G in the deep wells A localized high is centered in well MW-208 and the concentrations attenuate laterally to the locations of wells MW-202, MW-209 and MW-210 2 MTBE • Figure 8 illustrates the distribution of MTBE in the shallow (water table) wells ' Contours were not produced for the drawing because only well MW-7 contained MTBE (0 7 ug/l,dust above the laboratory reporting limit of 0 5 ug/L) • Figure 9 illustrates the distribution of MTBE in the intermediate wells A localized ' high of 17 3 [.g/1 is present in well MW-106 that attenuates west and east locations of MW-107 and MW-109, respectively • Figure 10 illustrates the distribution of MTBE in the deep wells A node of MTBE (4 µg/l) is present in well MW-209 that attenuates to the west, northwest and southwest locations of MW-202, MW-208 and MW-210 3 Benzene • None of the shallow wells contained Benzene above the laboratory reporting limits and therefore a contour diagram was not produced • Figure 11 illustrates the distribution of Benzene in the intermediate wells Contours were not produced for the drawing because none of the wells contained Benzene above the laboratory reporting limit of 0 5 ug/L ' o Figure 12 illustrates the distribution of Benzene in the deep wells Contours were not produced for the drawing because none of the wells contained Benzene above the laboratory reporting hmut of 0 5 ug/L Oxidation/Reduction Potential (ORP) and dissolved oxygen (DO) measurements (Table 6) show that 17 wells have low to highly negative ORP values and low DO readings The negative ORP values observed in the wells show that they are either within the core of the contamination plume or are in the reaction/depletion zone down gradient of the plume Dissolved oxygen values generally corroborate with the ORP values measured in these wells ' and suggest that the plume is relatively stable As indicated in Figure 13 —MW-2 TPH-G vs GW Elevation, with the exception of June 20, ' 1997, contaminant concentrations have generally mimicked the pattern of groundwater elevation changes for the past 10 years in down gradient well MW-2 1 3.0 CONCLUSIONS & RECOMMENDATIONS Based on our interpretation of the data collected over the course of this subsurface investigation, GTI has reached several conclusions These conclusions are based on the